Erhai Lake is the second largest freshwater lake on the Yunnan Plateau, Southwest China. In recent decades, a number of exotic fish species have been introduced into the lake and the fish community has changed conside...Erhai Lake is the second largest freshwater lake on the Yunnan Plateau, Southwest China. In recent decades, a number of exotic fish species have been introduced into the lake and the fish community has changed considerably. We evaluated the status of the fish community based on surveys with multimesh gillnet, trap net, and benthic fyke-net between May 2009 and April 2012. In addition, we evaluated the change in the community using historical data （1952-2010） describing the fish community and fishery harvest. The current fish community is dominated by small-sized fishes, including Pseudorasbora parva, Rhinogobius giurinus, Micropercops swinhonis, Hemiculter leucisculus, and Rhinogobius cliffordpopei. These accounted for 87.7% of the 22 546 total specimens collected. Omnivorous and carnivorous species dominated the community. A canonical correspondence analysis （CCA） plot revealed that the distribution of fishes in the lake is influenced by aquatic plants, water temperature, pH, and season. The abundance of indigenous species has declined sharply, and a majority of endemic species have been extirpated from the lake （a decrease from seven to two species）. In contrast, the number of exotic species has increased since the 1960s to a total of 22 at present. The fishery harvest decreased initially following the 1960s, but has since increased due to the introduction of non-native fish and stocking of native fish. The fishery harvest was significantly correlated with total nitrogen, not total phosphorus, during the past 20 years. Based on our results, we discuss recommendations for the restoration and conservation of the fish resources in Erhai Lake.展开更多
The feeding habits of 140 specimens of Carcharhinus brachyurus （Fam. Carcharhinidae） inhabiting Ain-EI-Ghazala lagoon on the Mediterranean Sea, eastern Libya were studied monthly from February to June 2013. The annu...The feeding habits of 140 specimens of Carcharhinus brachyurus （Fam. Carcharhinidae） inhabiting Ain-EI-Ghazala lagoon on the Mediterranean Sea, eastern Libya were studied monthly from February to June 2013. The annual diet composition, monthly variations in the diet composition, the variations of diet with length and the intensity of feeding were studied. Carcharhinus brachyurus feed on a wide variety of prey types： Pelagic bony fishes （54.5%）, benthic bony fishes （36.4%）, Cephalopods （6.8%）, Cartilaginous fishes （1.7%） and Fish parts （0.6%）. The Pelagic bony fishes and benthic bony fishes were the major food items during the study period in question, and they were found in all length groups. According to the results that were gleamed from this study, when the size of the sharks increased, the proportion of pelagic bony fishes within the sharks＇ stomachs grew in size, while the benthic bony fishes and Cephalopods decreased in size. The feeding intensity was quite high during the winter, spring and summer, this study is the first to study the Elasmobranchs in Libya, and it will be good base to study another species, specifically.展开更多
基金Supported by the National Special Research Fund for Non-Profit Sector(Agriculture)(No.200903048-04)the Major Science and Technology Program for Water Pollution Control and Treatment of China(No.2012ZX07105-004)the State Key Program of National Natural Science Foundation of China(No.30830025)
文摘Erhai Lake is the second largest freshwater lake on the Yunnan Plateau, Southwest China. In recent decades, a number of exotic fish species have been introduced into the lake and the fish community has changed considerably. We evaluated the status of the fish community based on surveys with multimesh gillnet, trap net, and benthic fyke-net between May 2009 and April 2012. In addition, we evaluated the change in the community using historical data （1952-2010） describing the fish community and fishery harvest. The current fish community is dominated by small-sized fishes, including Pseudorasbora parva, Rhinogobius giurinus, Micropercops swinhonis, Hemiculter leucisculus, and Rhinogobius cliffordpopei. These accounted for 87.7% of the 22 546 total specimens collected. Omnivorous and carnivorous species dominated the community. A canonical correspondence analysis （CCA） plot revealed that the distribution of fishes in the lake is influenced by aquatic plants, water temperature, pH, and season. The abundance of indigenous species has declined sharply, and a majority of endemic species have been extirpated from the lake （a decrease from seven to two species）. In contrast, the number of exotic species has increased since the 1960s to a total of 22 at present. The fishery harvest decreased initially following the 1960s, but has since increased due to the introduction of non-native fish and stocking of native fish. The fishery harvest was significantly correlated with total nitrogen, not total phosphorus, during the past 20 years. Based on our results, we discuss recommendations for the restoration and conservation of the fish resources in Erhai Lake.
文摘The feeding habits of 140 specimens of Carcharhinus brachyurus （Fam. Carcharhinidae） inhabiting Ain-EI-Ghazala lagoon on the Mediterranean Sea, eastern Libya were studied monthly from February to June 2013. The annual diet composition, monthly variations in the diet composition, the variations of diet with length and the intensity of feeding were studied. Carcharhinus brachyurus feed on a wide variety of prey types： Pelagic bony fishes （54.5%）, benthic bony fishes （36.4%）, Cephalopods （6.8%）, Cartilaginous fishes （1.7%） and Fish parts （0.6%）. The Pelagic bony fishes and benthic bony fishes were the major food items during the study period in question, and they were found in all length groups. According to the results that were gleamed from this study, when the size of the sharks increased, the proportion of pelagic bony fishes within the sharks＇ stomachs grew in size, while the benthic bony fishes and Cephalopods decreased in size. The feeding intensity was quite high during the winter, spring and summer, this study is the first to study the Elasmobranchs in Libya, and it will be good base to study another species, specifically.
